In the 1950s, the Soviet scientist Ilizarov invented the ring type of bone external fixator. Through a lot of clinical practice and basic research, it was found that stable and slow distraction could stimulate the biosynthesis and cell proliferation of living tissues, and finally the tension-stress law was formed. The main clinical applications are.
(1) Percutaneous closure for fractures of the backbone and epiphysis.
(2) Phase I repair of a wide range of bone, nerve, vascular and soft tissue defects without tissue grafting.
(3) Bone thickening for functional and cosmetic needs.
(4) Percutaneous one-stage treatment of congenital and post-traumatic pseudarthrosis.
(5) Limb lengthening or blockage of bone growth.
(6) Correction of bone and joint deformity, and correction of horseshoe foot deformity.
(7) Treatment of joint contracture.
(8) Arthroplasty.
(9) Percutaneous joint fusion.
(10) Treatment of bone cysts and osteonecrosis.
(11) Treatment of open bone defects and bone discontinuity.
(12) Treatment of osteomyelitis.
(13) Lengthening of amputated limb stump.
(14) Dysplasia of the mandible and other bones.
(15) Occlusive vasculitis.
(16) Treatment of chondrodysplasia and dwarfism, etc.
I. Main technical principles.
1.Stable fixation.
To maintain stable fixation of the bone segment, a stable framework should ensure both a reasonable mechanical and biological environment for the fracture end and maintain the weight-bearing exercise of the limb and the recovery of joint function. Overly strong fixation limits micromovement of the broken bone end and is detrimental to fracture healing. Unstable fixation and inappropriate bone segment movement impairs local microcirculation, impairs fracture healing, and leads to osteogenesis through fibrocartilage. Reliable fixation, early weight-bearing and active muscle function exercises increase local blood supply and shorten the process of bone scab formation and shaping. The external fixator is fixed to the bone by means of steel pins, and the key to determine the degree of stability of fixation depends on: (1) the number of steel pins.
(2) The angle between the two pins.
(3) The diameter and number of fixation rings and the span between the rings.
(4) The stiffness of the fixation structure.
(5) Density and shape of the bone and needle penetration site.
(6) The uncoordinated forces assumed by the frame configuration during distraction and compression.
(7) The shape and level of the fracture and osteotomy relative to the longitudinal axis of the bone.
(8) Soft tissues such as myofascia and ligaments attached to the bone segment.
(9) The strength of the limb muscles.
Also, the degree of stability of fixation depends on the understanding of the biomechanics of the external fixation device and the concept of correction. Inappropriate fixation not only results in reduced formation of new bone, but also causes discomfort to the patient and increases the chances of pin tract infection. The patient’s pain restricts the limb functional exercise and joint activity, reduces the weight bearing of the limb, gradually causes osteoporosis and makes the external fixation loose; the loosening of the external fixation further hinders the limb functional exercise, aggravates the discomfort of the limb, and simultaneously leads to the nutritional disorder of the limb, causing poor blood circulation, limb swelling, joint stiffness and aggravation of osteoporosis.
2, the principle of needle penetration.
Familiar with the anatomy of blood vessels, nerves, muscles, ligaments and synovial membranes, you can penetrate the steel needle in any part of the long bone.
The primary principle of needle penetration is to prevent thermal burns to the skin, soft tissues and bone caused by the process of penetrating the cortical bone. To reduce thermal burns, a flat prismatic tip (bayonet-shaped wire tip) can be used when penetrating the cortical bone stem instead of a trigonous tip; to further reduce thermal burns, an intermittent pause should be taken during penetration.
The second principle is that the steel needle should be kept perpendicular to the backbone through the soft tissue before threading, and after the needle tip penetrates the contralateral cortex, the tail of the needle should be struck with a hammer to penetrate the contralateral soft tissue so as to avoid damage to the soft tissue caused by rotating the needle tip.
Third, from the mechanical mechanics point of view, vertical cross-piercing pin fixation can obtain the most reasonable stability of the steel ring; while due to anatomical and functional limitations, the angle of cross-piercing pins usually cannot be vertical but smaller, and often auxiliary pins are needed to improve the stability of each plane of the frame.
Fourth, to ensure maximum joint mobility, care needs to be taken to keep the muscle extended when penetrating the muscle, to flex the adjacent joint when penetrating the extensor muscle, and to straighten the adjacent joint when penetrating the flexor muscle.
Fifth, before penetrating the needle, pay attention to the adjustment of the skin position. If the compression of the bone end is to be carried out, the skin position of the needle channel should be appropriately far from the osteotomy; on the contrary, when performing limb and bone lengthening, the skin of the needle channel should tend to the osteotomy site, so that the maximum available skin elasticity can be maintained.
3, the steel needle and steel ring fixation …… limb lengthening, should be considered according to the different muscle resistance to the balance of different planes of the limb instruments. For example, when the calf is lengthened, because there is a strong myofascial resistance against extension generated on the lateral side of the calf than on the medial side, therefore, in order to prevent the valgus deformity caused by the distraction, the steel pin and steel ring at the proximal end of the tibia should be inclined 10° to the medial side to counteract the tendency of the bone to valgus into the angle during the distraction. Similarly, the sagittal plane may cause angular deformity of the anterior arch due to strong resistance of the calf gastrocnemius muscle. In turn, greater resistance exists in the soft tissues on the concave side when correcting angular deformities. The configuration and installation of the appliance must be consistent with the running and alignment of the bone segment, otherwise deviation of the mechanical axis of the bone segment and poor alignment of the broken end of the bone will occur.
Care should be taken when fixing the steel pin to the steel ring: ensure that the ring is in posture with the pin; if the pin is forcibly bent and fixed to the ring, this may lead to displacement of the bone end and compression necrosis of the soft tissue of the skin. The stability of the fixation can be ensured if a proper tension of the steel pin is maintained. Deformation of the steel pin will result in reduced tension and osteoporosis, and phased retensioning of the pin is required, especially when compression of the osteogenic bone and when bone lengthening has gained the desired length.
The number of steel rings in the frame depends on the characteristics of the fracture and osteotomy, as well as the inherent stability of the limb. In limb lengthening, the stability of the frame is facilitated by the inherent elastic tension of the soft tissues, and only one ring at the upper and lower ends is sufficient to maintain the stability of the frame. In oblique and comminuted fractures, the number of steel rings should be increased to reset and stabilize the broken end of the bone.
4. Removal of external fixation.
Before removing the ring external fixator, the compression or tension should be gradually removed to ensure that the frame connection and the nuts and screws are neutral and free of tension in any direction. The removal of the external fixator is based on: completion of treatment, performance of regenerated bone in the distraction gap and reliable healing of the fracture.
II. Other technical principles.
1. Preoperative preparation.
Ilizarov technique is usually used to treat some difficult orthopedic diseases. The preoperative planning is very important and complex, mainly including: determining the site of deformity, analyzing the bone defect and soft tissue, defining the mechanical and anatomical axis of the limb. From there, an appropriate management strategy is developed based on the corresponding biological and mechanical needs.
Pre-operative education and psychological counseling are also necessary, requiring the patient and family to understand the surgical options, the risks of treatment, the expected results, the longer treatment time (including: surgical and post-operative latency period, duration of distraction, bone healing period, rehabilitation after external fixation removal), pain tolerance of the external fixator, as well as the necessary post-operative external fixation adjustments, care of the pin tract, speed of distraction and functional exercises, brace wear, etc.
2. Osteotomy.
The osteotomy site is usually chosen at the epiphysis, which has a stronger bone regeneration capacity than the osteotomy of the diaphysis. Low-energy osteotomy should be used to protect the local blood circulation and periosteum. The protection of the periosteum is particularly important, and a large number of experiments have confirmed that the periosteum is the main contributor to distraction bone regeneration.
3.Drawing speed.
The speed of retraction, i.e. the length of bone and soft tissue lengthening (measured in centimeters) per day, depends on a variety of factors. Experimental studies have confirmed that 0.5-2.0 cm/day can induce good bone regeneration, and Ilizarov believes that 1 cm/day is more favorable for bone formation. However, in practice, the speed should be adjusted to the specific situation, for example, the speed should be slowed down when the cortical osteocortex is thick and the blood circulation on the bone surface is poor. Generally, adults should be retracted more slowly; children need to be retracted faster than 1 cm/day, especially in the proximal epiphysis, to avoid premature healing of the bone gap. For bone lengthening requiring simultaneous correction of angular deformities, special consideration should be given to selecting the appropriate retraction speed; it is important not to have premature bone healing on the convex side while not exceeding the potential vascular supply regeneration capacity on the concave side, resulting in poor bone regeneration. The effect of the draft speed on the soft tissues should also be considered; many times a draft speed of 1 cm/day seems too fast for muscles, ligaments, etc., while it is relatively tolerable for peripheral nerves. The frequency of distraction is usually classified as 4-6 times/day, which can reduce the patient’s pain and is more conducive to bone formation.
Third, clinical application.
1.Limb lengthening.
Ilizarov technique applied to limb lengthening has many unique advantages: (1) the external fixation framework is more stable; (2) limb lengthening can be done simultaneously with correction of combined deformities; (3) protection of adjacent joints can be achieved; (4) more daily activities are allowed; (5) lengthening over longer distances can be accomplished.
Limb lengthening may involve additional complications: pin tract infection and localized osteomyelitis; premature bone healing, delayed healing, non-healing, axial deviation bending and fracture; joint contracture, joint dislocation and articular cartilage degeneration; nerve damage and vascular injury; local edema; persistent pain; systemic hypertension; vegetative nerve disorder; fascial compartment syndrome; osteosarcoma and poor bone fiber structure; etc.
2. Deformity correction.
The biggest advantage of Ilizarov technique applied to limb deformity correction is that simultaneous correction of bone, soft tissue and joint deformity can be obtained, with low risk, little trauma, complete deformity correction and low recurrence rate. Prior to surgery, the deformity is carefully analyzed by clinical features and X-rays to determine the CORA centre of rotation of the angulation. The external fixation configuration with joint hinge and distraction screw should be designed according to the characteristics of the deformity, and attention should be paid to match the joint hinge with the state of the deformity during installation.
3.Bone discontinuity.
The advantages of Ilizarov technique for treatment of osteochondrosis are: stable fixation, high bone healing rate, no need to use bone graft to avoid damage to other parts, simultaneous correction of combined angular deformity, elimination of bone defect, removal of bone infection, and reconstruction of limb length, while ensuring good joint function and not limiting the weight-bearing exercise of the limb.
For hypertrophic bone discontinuity due to good local blood circulation, if there is no limb shortening, only compression of the bone end is performed; in case of combined limb shortening, lengthening of the bone end or intermittent compression and lengthening can be performed directly; in case of combined bone defect, bone segment slip technique should be used. For atrophic bone discontinuity due to atrophy of the bone end, poor local blood circulation, and low osteoinductive capacity, repeated stimulation can be performed by first pressurizing the bone end and then pulling; or removing atrophic necrotic bone and then, according to the corresponding situation, performing bone end compression, bone end slip, and lengthening of the bone and limb. If the bone discontinuity is combined with infection of bone and soft tissue, the infected bone should be removed first and the infection of soft tissue should be controlled to obtain a well-circulated bone end, and the treatment of bone end compression, bone end slip, and bone and limb lengthening can be implemented in stages or simultaneously.
4. Treatment of fracture.
Ilizarov technique has greater advantages in the treatment of high-energy fractures and near-joint fractures. Percutaneous needle penetration, stable fixation, and early weight-bearing exercises are beneficial to the healing of fracture, joint movement and recovery of limb function. The healing process of fracture can also be synchronized with the correction of existing deformities, and the healing of fracture can be obtained by applying bone segment slip and bone end compression techniques when combined with bone defects, thus avoiding the trauma and risk of bone grafting. The advantages of the Ilizarov technique are more evident in severe open injuries and combined soft tissue loss. With the mastery and understanding of Ilizarov technique, there is more room for the rescue and treatment of serious limb trauma.
5.Treatment of complex foot and ankle deformity.
Complex foot and ankle deformity is a multi-part and multi-directional deformity, which is difficult to be perfectly corrected by traditional methods, with great trauma, high risk, poor appearance and many poor functions. Through Ilizarov technique, the external fixed orthosis is designed and installed according to the deformity of the foot, and after surgery, the tense and contracted soft tissues of the foot and ankle are slowly pulled in a certain direction to rearrange the deformity of the bones and joints of the foot and ankle to a relatively normal position, thus obtaining a satisfactory correction of the deformity. No matter how poor the condition of the patient’s limb is, combined with local ulceration, infection, poor circulation, skin scarring, etc., the needle can be threaded and fixed. The speed of retraction and the degree of fit of the retractor to the limb can be adjusted at any time according to the situation, and the risks can be effectively controlled. As the tissue retraction can be regenerated, it can prevent the recurrence of deformity and further stiffening of soft tissue to the maximum extent.
6. Other applications.
With the improvement and development of the understanding of Ilizarov technique, its clinical application is becoming more and more extensive. It can also be used in orthopedics for the treatment of knee and elbow contracture, hip stiffness and femoral head necrosis, amputated limb stump lengthening, spinal deformity correction, limb function reconstruction of bone tumor, etc.; and it has also achieved promising results in other specialized fields such as oral surgery, brain surgery and vascular surgery, etc.
IV. Current problems.
The current problems of clinical application mainly focus on: how to accelerate bone formation and bone healing; stimulate muscle growth; simplify the needle penetration of external fixator, especially to minimize the penetration of the whole needle; the effective combination of intramedullary needle and other internal fixation materials with external fixation; the application of distraction regeneration method to the reconstruction of cruciate ligament; the treatment of some difficult orthopedic diseases, etc.